Method for the preparation of zinc sulphate solutions



Patented Nov. 7, 1933 METHOD FOR THE PREPARATION OF ZINC SULPHATESOLUTIONS William Henry Hannay and Frederick Eric Lee, Trail, BritishColumbia, Canada, assignors to The Consolidated Mining and SmeltingCompany of Canada, Limited, Montreal, Quebec, Canada, a corporation ofCanada No llrawing. Application November 28, 1931 Serial N0. 577,860

2 Claims.

Our invention relates to a method of preparing zinc sulphate solutionsfor hydro-metallurgical operations, characterized by the step ofadlusting the amount of cobalt to the free acid in the solution forinhibiting corrosion and disintegration of the anode and the entrainmentof lead in the deposited zinc without causing resolution effects orpreventing the deposit of coherent reguline zinc.

Complex zinc ores usually contain 'cobalt, and previous investigatorshave postulated that its presence in sulphate solutions, even in themost minute quantities, causes resolution effects and prevents thedeposition of coherent reguline zinc, and on that hypothesis thesolution, heretofore,- has been highly purified to completely eliminateit.

sults, while amounts in excess of them impair the efiiciency of the cellat a correspondingly increasing rate in proportion to the increase ofcobalt. A constant balance between the cobalt and the free acid of thesolution must therefore be maintained either by purifying the solutionwhen the cobalt fraction exceeds the correct ratio, or by adding cobaltwhen it is necessary to bring it up to that ratio, and this balance isduction and sale price of the zinc, particularly in the operation orlarge zinc extraction plants, having several thousand lead anodes inconstant use..

we claim as new and desire to secure by letters Patent is:

v 1. A hydro-metallurgical method fOl' the electrolytic deposition ofzinc from a sulphate solu- We found, however, that when a lead anode isused in the electrolysis of such solutions the zinc deposited at thecathode contained lead detached from the anode by corrosion, and thatthe corrosion is largely, if not wholly, due to the absence of cobalt inthe electrolyte.

The useful life of the lead'anode in the electrolysis of a sulphatesolution 'in which there is in the electrolysis, the step ofincorporating cobalt in the solution in the proportion of from i tosmilligrams of cobalt per litre of solution containing approximately 10%free acid, andthereafter maintaining said specified ratio balance einocobalt present does not average more than ther by purification of thesolution under treatthree months and when it is present in the solumentor by increasing the cobalt content. tion its useful life averages aboutthree years. 2. A hydro-metallurgical method for the elec- When theamount of cobalt is properly adjusted trolytic deposition of zinc from asulphate soluto the free acid of the solution there is neither tion whenusing a lead anode which comprises corrosion of the anode nor lead inthe zinc and maintaining the cobalt-acid ratio in the solution noresolution efl'ects to prevent the deposit of counder treatment withinsuch limitsthat at no herent reguline zinc. time does the cobalt contentrecede below a mini- The optimum amount of cobalt in the solution mum offrom 4 to 6 milligrams per litre of soluaccording to this adjustment, ismaintained betion containing 10% free acid solution or exceed tween 4and 6 milligrams per litre containing apa maximum of 15 milligrams perlitre of solution proximately 10% free sulphuric acid and up tocontaining 7 to 8% free acid. 15 milligrams of cobalt per litreiifsulphate solutions containing 7 or 8% free acid. Amounts be- WILLIAMHENRY HANNAY. low these ratios have no material beneficial re- FREDERICKERIC, LEE.

an important factor governing the cost of pro- Having thus fullydescribed our invention, what tion which comprises, when using a leadanode

